1. Field of the Invention
The present invention relates to a percussion electrical hand-held tool such as a combihammer or a chisel hammer.
2. Description of the Prior Act
Percussion electrical hand-held tools, which apply blows to a working tool, because of their interaction with a workpiece and the hand-arm-system of the tool user, and because of the mass and stiffness distribution, have a very complex self-excitation. The resulting self-vibrations, in particular in the region of the tool handle, should be suppressed to a most possible extent. The technical expenditure associated with passive damping or active controlled vibration suspending systems, increases with complexity of the to-be-compensated self-excitation.
European Publication EP-0107628 discloses a chisel hammer having a reluctance motor freely projecting along a rotor axis forming an extension of an eccentric of the percussion mechanism, i.e., the motor is arranged completely on one side of the percussion axis. In this chisel hammer, the center of gravity, which is offset from the percussion axis toward the reluctance motor leads, as a result of interaction with a workpiece and with the hand-arm-system of the user, to bending torques, which are very complex and differ from axial vibrations. In addition, the reluctance motor, which is directly connected with the eccentric, necessarily rotates slowly and, as a result, has a high, for a reluctance motor, mass/power ratio.
European Publication EP-1238759 discloses a chisel hammer having a percussion mechanism, and a symmetrical, to a most possible extent, with respect to the percussion axis, radial mass distribution. In this chisel hammer, the percussion mechanism drive gear is arranged, with respect to the percussion axis, diametrically relative to a portion of the motor. The space requirement of the motor in the core region of the percussion axis necessitates constructively a large axial spacing from the eccentric, which leads to generation of bending torques.
Accordingly, an object of the invention is a percussion electrical hand-held tool having an analytically simple, to a most possible extent, excitation.